Forensic analysis of spent bullets and cartridge cases by experts since at least the 1920's has provided law enforcement organizations with a very effective technique for solving crimes involving firearms. However, the process of comparison of markings on cartridge cases and bullets has always been a time consuming and complicated process for the ballistics expert. Typically, a trained ballistics expert or technician can spend one to two hours comparing just two different bullets or cartridge cases. A trained technician would have to spend a day or more to compare several bullets or shells. Because of the difficult nature of the process, law enforcement agencies in the past have only used analysis by comparison of bullets or cartridge cases when they were reasonably sure a match would exist or in preparation for trial, due to the time consuming and complex nature of the work. Thus, it was impractical if not impossible, to use comparison of cartridge cases and spent bullets in the initial investigative process. A typical crime scene today, where firearms have been used in the commission of a crime, can have a significant numbers of spent cartridge cases and bullets given the widespread availability of automatic and semi-automatic weapons. Thus, an important and significant need has existed for some time to automate and systematize the process of forensic analysis of spent bullets and cartridge cases to make it an effective investigative tool.
A number of significant developments have occurred over the last several years in the area of automated spent bullet and cartridge case analysis. In fact, the owner of the rights to the present application has been involved in a number of breakthrough developments in this field of technology. Some of the more significant developments are as follows:
U.S. Pat. No. 5,390,108 COMPUTER AUTOMATED BULLET ANALYSIS APPARATUS, and U.S. Pat. No. 5,659,489 METHOD AND APPARATUS FOR OBTAINING A SIGNATURE FROM A FIRED BULLET, incorporated herein by reference. These patents disclose an apparatus and method for automated analysis and comparison of spent bullets. The system produces images of the spent bullets, digitalizes those images, then stores the images for later electronic comparison to determine if a potential match exists between the subject bullet and similarly acquired images of bullets from the same or a different crime scene. Thus, with this system the tedious task of comparing spent bullets from many crime scenes is automated and the time needed to do the analysis drastically reduced.
U.S. Pat. No. 5,379,106 METHOD AND APPARATUS FOR MONITORING AND ADJUSTING THE POSITION OF AN ARTICLE UNDER OPTICAL OBSERVATION, incorporated herein by reference. This patent described among other things a method and apparatus for automating the positioning of a spent bullet for imaging.
U.S. Pat. No. 5,633,717 METHOD FOR MONITORING AND ADJUSTING THE POSITION OF AN OBJECT UNDER OPTICAL OBSERVATION FOR IMAGING, incorporated herein by reference. This patent disclosed another refinement for automating the positioning of an object for optical observation.
U.S. Pat. No. 5,654,801 FIRED CARTRIDGE EXAMINATION METHOD AND IMAGING APPARATUS, incorporated herein by reference. This patent provides an apparatus and method of illuminating the breech face of a cartridge case with axial symmetric lighting in order to obtain images of firing pin impressions on the breech face of a spent cartridge case.
The above systems provide the forensic scientist analyzing spent bullets and cartridge cases with effective tools for comparing spent bullets or cartridge cases in a variety of situations. The systems can be used to examine and analyze spent bullets from a specific crime scene with spent bullets or cartridge cases from a multitude of other crime scenes. Another use, among a number of possibilities, is in the examination of fired bullets or spent cartridge cases from a suspect firearm. Thus, the police in conducting an investigation of a crime scene from which it obtains spent bullets and/or cartridge cases have the ability to compare them with thousands of others from widely different crime scenes within a very short period of time. Naturally, a trained forensic ballistics expert has to make the final determination of whether or not a match exists between various bullets or shells. The inventions referred to above and the one described in this specification and its claims provide powerful analytical tools for standardized, systematized and automated analysis and comparison of literally thousands of cartridge cases and bullets in a matter of minutes and present the expert with a short list of the ones which offer the best match. In the list of potential matches it also provides a priority on those that make the best match. Thus with the inventions referred to herein the expert no longer has to individually handle, sift through and compare hundreds or thousands of possibilities. However, even before the expert examines the short list of potential matches the list itself provides significant leads to the police for their investigation.
The above patents generally relate to imaging and analyzing, with appropriate methods and apparatus, the markings left by a gun barrel on spent bullets, the impressions left by the breech face of a gun on the top of the head of the cartridge case and the impression left by the firing pin on the primer of a cartridge case. However, during loading, firing and ejection of a cartridge case the ejector mechanism of the gun also leaves a unique impression on the cartridge case. This results from the fact that during the manufacturing process of a firearm the machining and milling operations leave each ejector mechanism surface with slightly different engravings which are unique to the specific firearm.
The ejector mark which appears on the rear face of a cartridge case varies in depth and in degree of definition depending on the unique ejector mechanism of each firearm. The ejector mark usually starts at the edge of the rim of the top of the head of the cartridge case and generally extends in a linear direction across the cartridge case surface as the result of movement of the ejector. The ejector mark generally has a number of striations or other significant markings which give it a unique character and thus identify it a being made by the ejector mechanism of a specific firearm. However, given the location of the ejector mark and their general configuration and depth, imaging and lighting techniques and apparatus which have been developed for efficient standardized and systematized analysis and comparison as described in the above patents, and as now, practiced do not provide adequate means for obtaining good images which can be used for efficient standardized and systematized comparison and analysis of ejector mark images on cartridge cases obtained from a wide variety of locations and at different times. All of the above mentioned methods of lighting, have proved inadequate for obtaining necessary and useful images for standardized and systematized comparison and analysis of ejector mark. Accordingly, there is a need for an imaging system which can obtain useful images of an ejector mark for standardized and systematized comparison and analysis. There is also a need for a method and apparatus for properly positioning of a cartridge case for imaging of the ejector mark, which neither current practice, nor the above mentioned patents meet.